Controlled release composition and method of manufacturing same

ABSTRACT

Controlled release compositions are manufactured by subjecting cellulosic pulp rejects to a dewatering operation to remove approximately 25% of the water; flash-drying the obtained partially dewatered rejects, causing the rejects to expand and become porous; adding an additive material to impregnate the expanded and porous cellulosic material, and drying. The cellulosic material holds or retains the additive for delayed release. The compositions have good stability and structural integrity.

FIELD OF INVENTION AND BACKGROUND

The present invention is directed to controlled release compositions.More particularly, the invention is directed to an expanded, porous,cellulosic carrier material impregnated with an additive material forsubsequent release or chemical reaction, and to its process ofmanufacture. According to the present invention, cellulosic pulp rejectsfrom a papermill are partially dewatered; flash-dried to cause therejects to expand and become porous; an additive material to be slowlyreleased is applied to the expanded porous cellulosic rejects, and thendried. The cellulosic carrier material holds or retains the additive fordelayed release.

It is recognized that there are numerous compositions which arenecessarily or most advantageously applied for slow release over aperiod of time. Such compositions include fertilizers, plant growthstimulants, herbicides, pesticides, and fungicides. As a result of thisneed, various time or controlled release compositions have beenproposed. U.S. Pat. No. 4,388,352 discloses a time-released compositionwherein a carrier such as never-dried cellulosic pulp is immersed in asolution of an impregnant, such as a solution of fertilizer; the mixturedistilled to exchange the fluid in the pores of the carrier with thesolution of the impregnant, and thereafter the carrier is dried toentrap the impregnant within the pores. According to the patentdisclosure, during the distillation process the solution of impregnantdiffuses through the pulp to displace the water otherwise in the pores.The pulp is then dried. During the drying, the pores of the never-driedpulp irreversibly collapse. The collapse of the pores is the manner inwhich the impregnant is trapped within the pulp. Accordingly, thecarrier material in the final composition is not porous and, therefore,the additive material must pass through the carrier material forrelease.

U.S. Pat. No. 3,172,752 discloses a controlled release substance havingan active material such as a herbicide, fungicide or insecticidesuspended in or on perlite as a carrier material which is then coated.In the processing the carrier material is preheated to remove some ofthe water contained therein. Thereafter, the perlite is heated by meansof a hot gas and caused to expand. The expanded perlite particles,according to the patent, provide a relatively inert particulate base foran active material. A holding material is added to the composition sothat the additive material will more readily adhere to the perlite base.The holding material can be a material such as lignite, sea kelp,activated sewage sludge, or sulfide paper pulp liquor. Perlite, being ahard glasslike material, has limitations both from the standpoint of itstreatment and from its end uses.

U.S. Pat. No. 3,269,824 discloses a wastepaper soil conditioning andfertilizing pellet. According to the patent, wastepaper is repulped andwater is then added to it, and the mixture cooked under pressure into aslurry of finely divided cellulose fibers. Fertilizers and otherelements are then added to the slurry and thoroughly mixed. Theresultant composition is drained into a vacuum chamber where excessmoisture is drawn off until the slurry reaches the consistency of astiff dough. The slurry is then packed into a metal cylinder andextruded into strands which are then cut into pellets. Any moistureremaining in the pellets is removed by drying under infrared lamps asthe pellets move from the extrusion step along a conveyor belt. Uponapplication to soil, the moisture in the soil causes the densifiedpellets to expand gradually to double or triple their compressed volumewhile drying of the soil will cause the pellets to contract. The methodof manufacture is time-consuming and expensive.

Although the aforesaid methods and compositions are useful and each hascertain advantages, none is completely acceptable from the standpoint ofcost of materials and processing, stability and structural integrity ofthe composition, versatility of the carrier material so as to permit theuse of a single carrier material for a plurality of additive materials,or availability of the carrier materials in diverse locations so as topermit manufacture of the compositions at or close to the point of use.

OBJECTS AND GENERAL DESCRIPTION OF THE INVENTION

Accordingly, it is a primary object of the present invention to providea controlled release composition which is low in cost.

It is another primary object of the present invention to provide acontrolled release composition having good stability and structuralintegrity.

It is another object of the present invention to provide a controlledrelease composition which is versatile permitting the use of a singlecarrier material for the collection and retaining of a plurality ofadditive materials.

It is another primary object of the present invention to provide animproved method of making a controlled release composition which is lowin cost, has good stability and structural integrity and is versatile inpermitting the application and retaining of a variety of additivematerials to a carrier using a single process.

These and other objects of the invention will become apparent from thefollowing general description of the invention, the illustrativedrawing, and presently preferred detailed embodiment.

According to the present invention, cellulosic pulp rejects normallyrecovered from a pulpmill in a water slurry are dewatered to remove apart of the water. The partly dewatered pulp rejects are thenflash-dried, which expands and renders the rejects porous. In order toget adequate expansion and porosity, it is essential that the cellulosicpulp rejects at the time of flash-drying contain from about 40 to 70%water. The flash-drying is carried out in a conventional louvered rotarydryer such as a Heil or Aeroglide dryer at a temperature of from about400 to 700° F. The high temperature causes the water on and in thecellulosic rejects to rapidly vaporize, causing the rejects to expandand "explode," providing the desired porosity in the cellulosic carrier.After the flash-drying, the expanded rejects are transferred to acyclone storage bin from which they are fed to a sizer where they aresized and then fed to a blender. In the blender, the sized rejects areimpregnated with an additive material such as a fertilizer. After theimpregnation, the impregnated rejects are cooled and subjected to afinal drying to the extent necessary. The rejects are then fed to apackaging or bagging machine, or to a bulk storage bin.

According to the presently described invention, the carrier materialcomprises the cellulosic rejects of a papermaking plant. These rejectsare a by-product or waste product of the papermaking operation, andcomprise cellulosic fibers which are separated from the main body ofpulp during the treatment of the pulp in the papermaking process. Thesereject fibers are carried in large volumes of water, for example 5%fiber and 95% water. The fibers are separated from the water usingfiltration means. The separated cellulosic fibers, commonly referred toas "rejects," still contain up to about 85% water. Further, the rejectsare in the form of lumps or clumps of fibers. In the flash-drying of therejects, the lumps or clumps are broken up into small particles. Theseparticles are then impregnated with an additive material withoutsubstantial modification of the cellulosic particles. Accordingly, thereis an abundant, low-cost supply of carrier material in the vicinity ofevery papermaking mill.

The additive for application to the cellulosic carrier can be virtuallyany additive which is compatible with or which can be made compatiblewith the cellulosic rejects. Cellulosic rejects in water are hydrophilicand, therefore, will accept any naturally hydrophilic additive materialor material which has been treated, for example, with a surfactant toprovide compatibility. Alternatively, the cellulosic rejects can betreated to render them hydrophobic. The surfactants which are usefulinclude the nonionic, anionic, and cationic surfactants. The selectedsurfactant depends in part upon the additive material to be utilized.Suitable additives include fertilizers such as mixtures of nitrogen,phosphorus and potash; as well as insecticides, herbicides, fungicides,and plant growth stimulants, particularly those which are to be applieddirectly to the soil. In such applications not only does the cellulosiccarrier slowly release the additive over a period of time, but it actsas well to condition the soil. Over a period of time the carrier isassimilated into the soil to provide for aeration without packing and tohelp protect against erosion. Other additives for incorporation into thecellulosic rejects include pH-control materials to be used incompositions to be applied to the soil for controlling soil pH or forcontrol of pH in a pH-sensitive operation. For example, the cellulosiccarrier can be impregnated with an alkaline material such as sodiumhydroxide. The sodium hydroxide containing composition can be used as abarrier for an acid-containing aqueous slurry. As the slurry, forexample from an oil well, passes through the barrier, the acid containedin the slurry will be neutralized by the sodium hydroxide in thebarrier. As will be apparent to one skilled in the art, otherapplications can be realized.

DRAWING AND PRESENTLY PREFERRED EMBODIMENT

Having described the invention in general terms, a presently preferredand detailed embodiment will be set forth with reference to the drawing.

In the drawing, the sole figure is a flow diagram of the process formanufacturing the controlled release composition of the presentinvention. As illustrated in the drawing, papermill reject pulpcomprising about 85% water is subjected to a dewatering operation indewaterer 10 to remove approximately 25% of the total water.Accordingly, the cellulosic rejects after dewatering will contain about60% total water content. The dewaterer in the embodiment shown comprisesa continuously moving web having in association therewith first apressure roller, a spider mixer, and then a second pressure roller.

Also in the embodiment shown, pulp sizer and conditioner 12 is utilizedto treat the dewatered pulp before flash-drying with a nonionicsurfactant. A suitable nonionic surfactant is an ethylene oxidederivative of nonylphenol. The conditioned dewatered pulp is then fed toa flash dryer 16 where the cellulose is subjected to a temperature offrom about 400 to 700° F., at which temperature the water contained inthe reject pulp is rapidly volatilized, expanding the pulp reject andrendering the pulp porous. The flash dryer utilized in the embodimentillustrated is a conventional dryer having a gas burner 17 which permitsrapid heating and also heat dissipation.

The flash-dried cellulose rejects are then fed to a cyclone storage bin18 for storage until the materials are to be impregnated with anadditive material. The expanded cellulose is fed from bin 18 throughproduct valve 20 to a sizer 22 where the cellulosic particles areproperly sized. It is usually desirable that all of the particles for aparticular application have the same size within about a 20% range.Thus, depending upon the end application, one particle size may bepreferable over another. For fertilizers it has been found that apreferred size is such that the cellulosic carrier will pass through aTyler Standard Mesh of 8 to 4. This mesh corresponds to a 3/32 to 3/16of an inch particle. After the sizing and separation of the differentsizes depending upon the application, the cellulosic carrier is fed to ablender. In making a fertilizer, particles having a size of 3/32 to 3/16of an inch in diameter are fed to blender 24 and kept in continuousmotion with an auger 25 having baffles 26. While in continuous motion,the cellulosic particles are sprayed with a aqueous mixture of 20% byweight nitrogen, 20% by weight phosphorus, and 20% by weight potash. Asillustrated and in the preferred embodiment, a plurality of sprayers 28--such as an air sprayer having adjustable valves to control the supplyof air entering the mixing chamber within the sprayer where air andadditive are blended--are arranged along the top or side of the blender.After being impregnated and continuously mixed, the impregnatedcellulosic fibers are fed to a dryer-cooler 30, and from thedryer-cooler 30 either to a packaging facility 32, a bagging facility34, or to bulk storage 36.

The compositions of this invention slowly release the additive materialto the environment of use, particularly the soil. Further, thecompositions have structural integrity while being stored. They will,however, when applied to the soil become slowly assimilated by the soil,imparting aeration to the soil while helping prevent soil erosion.

As will be apparent to one skilled in the art, various modifications canbe made within the scope of the aforesaid description. Suchmodifications being within the ability of one skilled in the art form apart of the present invention and are embraced by the appended claims.

IT IS CLAIMED:
 1. A delayed release composition comprising as a carrierparticulate cellulosic pulp rejects which have been expanded andrendered porous by flash-drying pulp rejects having a water content offrom about 40 to 70% at a temperature of from about 400 to 700° F.; and,as an additive, up to about 90% of the flash-dried volume of saidcarrier of an additive material for delayed release distributed on andin said carrier.
 2. The composition of claim 1 wherein said carrierincludes a conditioner applied thereto prior to flash-drying.
 3. Thecomposition of claim 1 wherein said additive material is a fertilizer.4. The composition of claim 3 wherein said fertilizer is a mixture ofnitrogen, phosphorus, and potash.
 5. The composition of claim 1 whereinsaid additive is a fungicide.
 6. The composition of claim 1 wherein saidadditive is an insecticide.
 7. The composition of claim 1 wherein saidadditive is a plant growth stimulant.
 8. The composition of claim 1wherein said additive is a pH-control ingredient.
 9. The method ofmanufacturing a composition for delayed release of an additive materialcomprising the steps of (1) providing a cellulosic reject pulp havingfrom about 40 to 70% water; (2) flash-drying said reject cellulosic pulpat a temperature of from about 400 to 700° F. to expand and render saidparticulate rejects porous; (3) impregnating said expanded cellulosicpulp with an additive material; and (4) drying.
 10. The method ofmanufacture of claim 9 including the step of treating said cellulosicpulp reject before flash-drying with a conditioner.
 11. The method ofclaim 10 wherein said conditioner is a surfactant.
 12. The method ofclaim 9 wherein said impregnation is with a blender.
 13. The method ofclaim 9 wherein said additive material is a fertilizer.
 14. The methodof claim 13 wherein said fertilizer is a mixture of nitrogen,phosphorus, and potash.
 15. The method of claim 9 wherein said additivematerial is an insecticide.
 16. The method of claim 9 wherein saidadditive material is a fungicide.
 17. The method of claim 9 wherein saidadditive material is a plant growth stimulant.
 18. The method of claim 9wherein said additive material is a pH-control ingredient.